PRO-MELANIN CONCENTRATING HORMONE MESSENGER-RIBONUCLEIC-ACID AND PEPTIDES EXPRESSION IN PERIPHERAL-TISSUES OF THE RAT

Melanin-concentrating hormone (MCH) is a cyclic peptide which is predo minantly synthetized in the hypothalamus of fish and mammalian brains. In the present paper we examined the expression of MCH mRNA and pro-M CH-derived peptides, i.e. MCH and neuropeptide-(N)-glutamic acid (E) i soleucine (I) amide (NEI), in peripheral tissues of adult rodents. By means of polymerase chain reaction (PCR) of reverse-transcribed RNA, l ow levels of MCH gene transcripts were detected reliably in testis, st omach, and intestine of Sprague-Dawley and Wistar rats, whereas strong expression was found in hypothalamus. Subsequent sequence analysis of the PCR products verified the authenticity of MCH mRNA found in hypot halamus and stomach. The length of MCH RNA species was measured by Nor thern blot and multiple MCH RNA species were detected in both rat spec ies. Shortest polyadenylated tails were found in MCH RNAs isolated fro m the peripheral organs by comparison with hypothalamus MCH RNAs of Wi star rats. In order to localize MCH expression in gastrointestinal and genital tracts of Wistar rats we performed in situ hybridization with specific P-33-labeled oligoprobes joined to immunocytochemical studie s with rat MCH or NEI antisera. In testis, the MCH transcripts and pro -MCH-derived peptide immunoreactivities were found at the periphery of the seminiferous tubules, suggesting expression in Sertoli cells. Stu dies with MCH oligoprobes and antisera directed towards MCH, NEI and a lpha A-inhibin revealed similar pattern of expression in isolated Sert oli cells from Swiss mice, indicating that MCH RNA species were actual ly synthesized and translated in these cells. In the gastrointestinal (GI) tract, the cells expressing MCH RNA species and pro-MCH-derived p eptides were predominantly expressed in the antral portion of the stom ach and duodenum. Strikingly, distinct oligoprobes, recognizing antise nse MCH transcript, revealed a pattern of hybridization in the GI trac t similar to this observed with oligoprobes revealing the mature MCH m RNA. Furthermore, total RNA from the pyloric junction, duodenum, jejun um, ileum and hypothalamus as well appeared to contain RNA complementa ry to MCH mRNA suggesting therefore that antisense MCH RNA species may play a general role in regulation of MCH synthesis. Taken together, o ur present and previous data indicate that authentic MCH RNA species a nd translational products are expressed in various rodent tissues at t he periphery. The cellular location suggests that MCH and associated p eptides may play a role in spermatogenesis and in digestive processes.